Fly ash separation



Aug. 16, 1960 E. c. MxLLr-:R 2,949,099

` FLY ASH SEPARATION Filed'April 21, 1958 2 sheets-sheet 1 INVENToR asrle C. miller MM 4MM-ig@ Aug. 16, 1960 E. c. MILLER 2,949,099

FLY ASH SEPARATION Filed April 21, 1958 2 Sheets-Sheet 2 INVENTOR Earle C. mjlle 45mm/@M l 2,949,099 1C@ Patented Allg- 15 11960 FLY ASH sEPARA'noN Earle C. Miller, Worcester, Mass., assignor to Riley Stoker Ciprporation, Worcester, Mass., a corporation of Massac usetts Filed Apr. 21, 1958, Ser. No. 729,626

3 Claims. (Cl. 122-235) This invention relates to ily ash separation and more particularly rto apparatus arranged to remove particles of unburned fuel and the like from the gas ilow ofthe furnace of a steam generating unit.

In the generation of steam it is common practice to increases the heat transfer between the products of combus' tion and the water or steam in the tubes of the boiler by introducing into the ilow of gas la series of baflles which cause the gas to move sinuously across the bundles of tubes; however, with some types of fuel and with certain methods of firing the fuel, large amounts of ily ash and foreign matter are entrapped in the ilow of gas. These particles are extremely hard and are of an abrasive nature and, when the products of combustion are reversed over the boiler tubes, it quite often happens that the boiler tubes become quickly eroded. These and other diiliculties experienced with prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the present invention to provide a ily ash separating means for use in a steam generating unit to reduce appreciably the erosion of boiler tubes.

Another object of the invention is the provision of apparatus for removing ily ash from products of combustion in a steam generating unit and returning them to the furnace for more complete combustion.

A still further object of this invention is the provision of a ily Aash separating apparatus for use in a steam generating unit in which the elements of the apparatus may be readily replaced when necessary.

It is another object of the instant invention to provide 4 a ily ash separating means of simple construction which is readily manufactured from easily-obtained materials which is simple in construction, which may readily be installed in existing steam generating units or the like, and which is capable of a long life of useful service with a minimum of maintenance.

While the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying 'drawings forming a part thereof, in which:

Figure 1 is a vertical sectional view of a steam generat ing apparatus embodying the principles of the present invention,

Figure 2 is an enlargement of a portion of the apparatus shown in Figure l, and

Figure 3 is a view of the apparatus shown in Figure 2 taken on the line III-III of that ligure.

Referring iirstto Figure l, wherein are best shown the general features of the invention, a -steam generating unit, indicated generally by the reference numeral is shown as comprising a furnace 11, and a boiler 12 mounted in the usual supporting structure 13. The furnace 11 consists of -a front wall 14, a rear wall 15, and sidewalls 16 defining a combustion chamber 17. On lthe front wall 14 are mounted fuel burning apparatus such as an intertube burner 18 and a spreader Stoker `19. Underlying the combustion chamber 17 is a traveling grate 21 discharging into an ash pit 22 and having an air plenum chamber 23 underlying its lower run. The boiler 12 consists of a steam-andwater drum 21 and a mud drum 25 joined by downcomer tubes 26. Connections are made between the mud drum 25 and headers 27 and 28 lying at the bottom of the cornbustion chamber 17. Water wall tubes 29 rise vertically from these headers and cover the walls 14, 15, and 16 of the furnace 11. The tubes of the boiler are so configured `as to form a horizontal upper pass 31 extending at right anglesto the top of the combustion chamber 17 and containing a high temperature superheater 32. A vertical baille 33 extends vertically downwardly from the steam-and-water drum 24 and forms a downpass 34 in which is located a low temperature superheater 35. The mud drum 25 is located below the lower end of the baille 33 and is separated therefrom by a considerable distance. A hopper 35 lies between the rear wall 15 of the furnace and the mud drum 25. The space between the mud drum 25 and the lower end of the baille 33 affords an entrance into a back pass 36 formed between the baille 33 and a back wall 37 of the unit. The back pass 36 contains the downcomer tubes 26 and is also provided with bailles 38 which extend from the baille 33 rearwardly and from the back wall 37 forwardly to produce a sinuous ilow of gases over` the tubes 26. A passage at the upper pant of the back pass 36 leads to the upper end of an economizer 39 of the usual type and the lower end of this is connected tothe stack, not shown, in the usual manner.

Underlying the back p-ass 36 and extending between the mud drum 25 and the back wall 37 is a hopper 41. Mounted on the rear part of the supporting structure 13 is a fan 42 driven by an electric motor 43 and having attached to its output a duct 44 which extends upwardly and then horizontally to pass under the hoppers 41 and 35 and terminate at the rear wall 15 of the furnace by connection to a series of overfire air nozzles 45. Suitable connections are made from the hoppers 35 and 41 to the duct 44. Situated in the lower part of the iirst pass 34 and overlying the hopper 35 is a separator 46 supported at its lower end on beams 47 extending between the mud drum 25 and the back wall 15. At its upper end the separator 46 is attached to the forward side of the baille 33.

Referring next to Figures 2 and 3, which show the details of the separator 46, it can be seen that separator consists mainly of a series of steel pipes 48 arranged side by side in slightly spaced relationship. The tubes extend transversely of the furnace and parallel to the steam-and-water drum 24 and they rest on a series of inclined angles 49 which are welded to water tubes 51 forming part of the baille 33. The lower ends of the angles 49 are welded to the beams 47. 'Extending upwardly from the angles 49 are a series of steel pegs 52 which serve to locate the pipes 48 and maintain them in spaced relationship. Overlying the pipes 48 are a series of angle irons 53 which serve to clamp the pipes to the upper surface of the angles 49 and this is accomplished by means of bolts 54 which extend through the angles 53 between the pipes 48 into the angle irons 49. As is evident in Figure 3, a number of inclined braces 55 extend between the angle irons 49 to maintain them in spaced rigid relationship. Furthermore, each of the tubes 48 is provided with a slip joint 56 consisting of a peg '57 welded in one end of a section of the tube and slidably fitted in the end of the other section of the tube. Fastened to the rear surface of the rear wall 15 of the furnace 11 is a plate 56 which extends downwardly and rearwardly with its end above and spaced from the lower end of the separator 46. A vane 58 is attached in the lower end of the plate 56 by means of a hinge 57. The vane being moveable from a position closely adjacent the lower end of the separator 46 to another position generally parallel to the rear Wall 15 of the furnace. The vane may be actuated externally of the steam lgenerating unit in the usual manner.

The operation of the apparatus will now be readily understood -in view of the above description. Fuel emanating from the burner 13 and the spreader Stoker i9 are burned in the combustion chamber i7 and the products of combustion flow upwardly in the combustion chamber and leave through the horizontal pass 3l. The products of combustion then move downwardly through the lirst pass 34 and are reversed in the lower portion thereof and pass through the space between the lower end of the baille 33 and the mud drum 25. The gases then move upwardly through the backpass 36 in a sinuous ow over the tubes 26, the liow being determined by the batlles 38. The gases then leave the unit in the usual manner through the stack. Water, of course, lows from the steam-and-water drum 24 downwardly through the downcomer tubes 26 into the mud drum 2S where it is distributed to headers 27 and Z8 and moves upwardly through the water wall tubes 29. Steam generated in the tubes is released in the steam-and-water drum 24 and is eventually superheated in the primary superheater 35 and the secondary superheater 32 before passing to the turbine, not shown, in which steam energy is converted to mechanical energy. As the tubes move downwardly through the ilrst pass 34 they eventually strike the separator 46 and pass between the tubes. Because of the pressure drop which occurs behind the tubes, according to the usual aerodynamic principles, it is possible for the ily ash and other line matter to agglomerate and fail downwardly into the hopper 35. Because of the resistance introduced into the ilow of gases by the separator 46, a high rate of llow may be produced in the space between the lower end of the separator 46 and the vane S by moving the vane slightly away from its position against the separator. It is well known that the greatest proportion of ily ash particles reside at the outer part of any reversal of ilow, this being brought about by centrifugal force. Therefore, by permitting this portion of the ilow of gases to ilow into the hopper 35 by means of manipulation of the vane 52 it is possible to remove a considerable portion of the ily ash in this way. Therefore, the gases which enter the bacltpass 36 through the opening between the lower end of the baille 33 and the mud drum 25 are comparatively free of ily ash. Because of the downwardly directed position of the lowermost baille 38 there is a reversal of gases above the hopper 41 which produces further fallout or" ily ash. The fan 24 produces a flow of air through the duct 44 and outwardly into the combustion chamber 17 through the ovenre nozzles 45. The llow of air through the duct 44 picks up ily ash from the hoppers 35 and 41 and projects it into the furnace where it takes part in the combustion process, some falling onto the traveling grate 21 for movement into the ash pit 22.

The ruse of the pegs 52 as a sepa-rating means for the tubes 48 of the separator 46 brings about a very accurate spacing of the tubes and makes the separator aerodynamically accurate. At the same time, the short angle irons 53 may be readily removed by loosening the bolts 54- to permit removal of the tubes 48 and replacement thereof. It will be understood that the telcscoping connection 56 permits each tube to be slightly shortened so that it may be removed from the boiler setting without cutting the tubes and without removing a portion of the boiler setting. The replacement of tubes must take place, of course, when the steam generating unit is shut down.

While certain novel features of this invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made in the forms and details of the device illustrated and in its operation without departing from the material spirit of the invention.

The invention having been thus described, what is called new and desired to secure by Letters Patent is:

l. A steam generating unit, comprising a combustion chamber having front, rear, and side walls, a horizontal convection passage extending away from the chamber and overlying the rear back Wall of the chamber, a first passage extending downwardly from the said convection passage behind the said rear wall of the chamber, a second horizontal passage extending rearwardly from the lower end of the said first passage, a back passage extending upwardly from the second horizontal passage, a series of batlles causing the products of combustion to tlow sinuously through the said back passage, the said second horizontal passage causing a radical change of direction of the products of combustion in passing from the first passage to the back passage, a hopper located adjacent the said second horizontal passage and generally in line with the original direction of the products of combustion as they pass downwardly through the lirst passage, and a separator through which the gas is passed during the said reversal located adjacent the hopper and lying in a plane inclined substantially to the original direction with its lower end located adjacent the said rear wall of the combustion chamber opposite the second horizontal passage, a narrow opening between the lower end of the separator and the said rear wall of the combustion chamber, and a damper mounted in the said opening to control the passage of gas therethrough.

2. A steam generating unit comprising a combustion chamber from which originate products of combustion containing ilyash, the chamber having front, rear, and side walls, a horizontal convection passage extending away from the chamber and overlying the rear wall of the chamber, a tirst passage extending downwardly from the convection passage behind the said rear wall `of the chamber, a seco'nd horizontal passage extending rearwardly from the lower end of the said rst passage, a back passage extending upwardly from the second horizontal passage, a series of bales located in the back passage causing the products of combustion to flow sinuously therethrough, the second horizontal passage causing a radical change of direction of the products of combustion as they pass from the first passage to the back passage, a hopper located adjacent the said second horizontal passage and generally in line with the original directio'n of the products of combustion before the said reversal of direction, and a separator consisting of a series of tubes arranged transversely of the unit and in spaced parallel relationship, the gases passing between the tubes during the said reversal, the separator being located ad jacent said hopper and the tubes lying a plane inclined substantially to the said original direction with its lower end adjacent the said rear wall of the combustion chamber, the separator including a number o'f supporting elements extending under the tubes at right angles to the axes thereof, pegs extending upwardly from the said supporting elements and serving to maintain the tubes in spaced relationship, a narrow opening between the lower end of the separator and the said rear wall of the combustion chamber, and a damper mounted in the said opening to co'ntrol the passage of gases therethrough.

3. A steam generating unit, comprising a combustion chamber having front, rear, and side walls, a horizontal convection passage extending away from the chamber and overlying the rear wall of the chamber, a first passage extending downwardly from the convection passage behind the said rear wall of the chamber, a second ho'rizontal passage extending rearwardly from the lower end of the said first passage, a back passage extending upwardly from the second horizontal passage, a series of battles causing the products of combustion to flow sinuously through the said back passage, the said second horizontal passage causing a change of direction of the products of combustion as they pass between the rst passage and the back passage, a hopper located adjacent the said second horizontal passage and generally in line with the original direction of the products of combustio'n before the said reversal of direction as they pass downwardly through the rst passage, and a series of spaced, parallel, cylindrical elements through which the gases pass during the said reversal, and said elements being located adjacent said hopper and lying in a plane inclined substantially to the said original direction with their lower ends located ad- 6 jacent the said rear wall df the combustion chamber, and adjustable means for causing a portion of the gases to pass around the said series at the said lower end, the said portion of the gases containing a high portion of the 5 yash.

References Cited in the le of this patent UNITED STATES PATENTS 10 2,065,554 Beers Dec. 29, 1936 2,189,234 Wagner Feb. 6, 1940 2,265,091 Tongeren Dec. 2, 1941 

